Composite structures comprising particulate material in a particular pattern are well known in the art, see, e.g. EP-1447066 (Busam et al.; P&G), disclosing an absorbent core for an absorbent article, which has a particulate absorbent material that is immobilized when wet. The absorbent core comprises a substrate layer with an absorbent material, such as an absorbent polymer material.
U.S. Pat. No. 4,381,783 (Elias) discloses an absorbent article with a core comprising pockets of absorbent hydrocolloid material. These pockets are provided to confine the movement of absorbent polymer material, in particular when the article is fully or partially loaded with urine. The pockets form part of an absorbent layer and are typically provided from cellulose material. Hence, as to achieve good immobilization of the absorbent polymer material according to the teaching of this patent relatively high amount of cellulosic material is required. Moreover, the provision of such pockets may hinder the free distribution of liquid to the more absorbent areas of the core, for example the areas of the absorbent polymer materials.
Accordingly, processes to produce absorbent article having a non-homogeneous distribution of absorbent materials such as particulate absorbent polymer material, often referred to as absorbent gelling material or as superabsorbent, are also well known. In WO 03/101622A2 (Tombült et al.; P&G) a pulsing process for creating discontinuous particulate distribution is disclosed, and a similar structure may be produced according to U.S. Pat. No. 5,213,817 (Pelley; McNeill PPC).
Processes aiming at depositing a pattern of particulate absorbent material onto a web are described in U.S. Pat. No. 4,800,102 (Takada; Nordson), employing a rotating mask, or in WO 92/019198A (Perneborn/M∅lnlycke) showing a linearly moving mask. FR-A-2583377 (Piron; Colgate Palmolive) discloses a metering drum into which absorbent powder is fed from a hopper for creating discontinuous pattern on a carrier on a conveyor belt. The drum is operated in a step-wise movement.
U.S. Pat. No. 5,494,622 (Heath et al.; K-C), aims at producing pockets of particles in a desired pattern on a web moving at high speed. A pattern chamber is supplied with particles of high absorbency material through which a gas permeable web is transported on a surface having a pattern of openings through which a vacuum is drawn so as to cause the particles to be deposited on the web in the pattern of the openings in the surface. The web carrying the particles is covered by a layer of liquid permeable material or the tension applied to the permeable web is varied to vary the porosity of the web. The particles are held on the web in the desired pattern of pockets while surplus particles between the pockets are removed. The thusly formed pockets form “islands”, i.e. they are completely surrounded by bonded regions.
Whilst such documents describe various approaches to the deposition of particulate material onto a surface or on a moving substrate, there is still the need for a method to produce patterned particulate sandwiches in a very well defined pattern and at high production speeds.